Xrdp project request exporting this function again, because (unlike the
usual xf86-video-* drivers) they need their own custom cursor handling:
RDP is designed to draw cursors on client side.
Also documenting what the function does.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1787>